1. Field of the Invention
This invention relates to a tape recorder provided with a counter-display section which electronically calculates and displays the length of the wound portion of a rotated magnetic tape and the current time of the day by applying a different power source from that of a tape run control section.
2. Prior Art of the Invention
In recent years there have been developed various types of compact tape recorder which are provided with a time-counting function and designed to measure and display the current time of the day and the length of the wound portion of a rotated magnetic tape by means of a photoelectric display using, for example, a light-emitting diode (abbreviated as "LED") or liqud crystal.
Such compact tape recorder known to data performs many functions by a single power source. Therefore, a cell used as a power source has a short effective life. For example, two 1.5 volt miniature dry cells used with a compact tape recorder comprising a miniature cassette have an overall effective life of only about 11 hours. Each time the cell life is exhausted, the time-counting function of said tape recorder is stopped, giving rise to considerable inconvenience. Accordingly, it has been contemplated to apply different power sources for the original functions of a tape recorder itself and the operation of a built-in device for counting the current time of the day and carrying out a photoelectric display thereof.
FIG. 1 shows the circuit arrangement of a prior art tape recorder provided with a power source for a tape recorder itself and another power source for a time-counting and photoelectric display function.
A section 11 for measuring the length of the wound portion of a rotated magnetic tape (hereinafter referred to as "a tape run-measuring section") comprises a reel 12 for the takeup or feed of the magnetic tape; a disc 13 securely fixed to the reel 12; a plurality of magnetics 14, 15 equidistantly arranged on the peripheral surface portion of the disc 13; and a lead switch 16 set at a point alternately approached by the magnets 14, 15. The tape run-measuring section 11 issues pulse signals in a number corresponding to the run of a magnetic tape at the time of, for example, recording, reproduction, quick feed or unwinding. While the tape recorder is in operation, the lead switch 16 is alternately closed and opened by the magnets 14, 15 mounted on the disc 13. Pulse signals issued from the tape run-measuring section 11 when the switch 16 is closed are supplied to a counting section 17. This counting section 17 is formed of a pullup resistor 18, field effect transistor 19 and counter 29. This counter 29 comprises, for example, an adding/subtracting circuit and totaling circuit. The counting section 17 counts pulse signals received. A signal denoting a counted number of pulses is conducted to a display device 24 through a mode changeover switch 20 (which is connected to a contact 21 at this time) and a decoder-driver circuit 23. The mode changeover switch 20 is used to carry out a changeover of operation mode between the measurement of the traveling distance of a magnetic tape and the display of the current time of the day. The decoder/driver circuit 23 decodes an output signal from the counter 29. The decoded signal is sent forth to the display device 24, which in turn indicates the measured tape run.
An output signal from an oscillator 25 is supplied to a time-counting circuit 27 through a frequency divider 26. Where the mode changeover switch 20 is connected to a contact 22, then an output signal from the time-counting circuit 27 is delivered to the display device 24 through the decoder-driver circuit 23.
The positive side of a display power source 28 is connected to the power supply terminals of the tape run-counting section, decoder/driver circuit 23, display device 24, oscillator 25, frequency divider 26, and time-counting circuit 27.
The positive side of a tape recorder power source 31 is connected through a tape recorder main switch 32 to the power supply terminals of an audio amplifier 33 and motor drive control circuit 34. The output terminal of said control circuit 34 is connected to a motor 35.
The magnetic tape takeup (or feed) reel 12 is rotated by a drive transmission device (not shown) driven by the motor 35. In this case, a cell for a time-counting function is likely to be unnecessarily depleted.
The run of a magnetic tape is measured by mounting a magnet on a rotor such as a magnetic tape takeup (or feed) reel, providing a lead switch at a point approached by the magnet, and counting a number of pulses issued from the lead switch by a counting circuit. However, the rotor fitted with the magnet does not always stop at a prescribed point. Sometimes, therefore, the rotor may be brought to rest at the point at which the lead switch would be rendered conducting. For convenience, FIG. 1 indicates only two magnets. Practically, however, a large number of magnets are equidistantly arranged. Therefore, the possibility grows large that the rotor stops at the aforesaid point at which the lead switch would be put into operation, thus unnecessarily depleting the capacity of a cell for a time-counting function.